1. Field of the Invention
The present invention relates to a crane apparatus which is used, for example, as a transfer crane of port cargo handling equipment.
2. Description of the Related Art
A conventional transfer crane has a gantry-shaped body frame, which can travel by a plurality of traveling wheels. On the top of the body frame, a trolley can move transversely. On the trolley, a rotationally drivable takeup drum is connected. A hoisting accessory is attached to the lower end of a plurality of load suspending wire ropes wound off from the takeup drum. Thus, as the trolley moves on the body frame, a suspended load held by the hoisting accessory can be traversed. When the takeup drum is rotationally driven at a predetermined stop position of the trolley to take up or pay out the plural wire ropes, the suspended load can be moved upwards or downwards.
With the above-described conventional crane apparatus, rails are provided on transverse girders placed on the body frame, and the trolley is supported on the rails. In con sideration of the weight of the rails, the weight of the trolley, or the weight of the suspended load imposed on the hoisting accessory, not only the transverse girders and the body frame, but also the entire crane apparatus must have great rigidity, inducing a large size and a heavy weight. When the trolley is moved laterally and stopped at a predetermined position, with the suspended load being held by the hoisting accessory, sway occurs in the hoisting accessory and the suspended load owing to an inertial force in the lateral direction. This sway does not settle quickly. To prevent sway of the hoisting accessory and the suspended load when the trolley stops, the trolley has to be moved at a slow speed. Since a long time is required for work, the work efficiency is low.
As a solution to the above-mentioned problem, a crane apparatus as shown, for example, in FIG. 4 is available. It should be noted that the numbering scheme for FIG. 4 and all other figures uses the numbers (n, nxe2x80x2) to designate pairs of like parts disposed orthogonally to the plane of the two-dimensional figure. In this conventional crane apparatus, as shown in FIG. 4, a pair of left and a pair of right traverser drums 101, 101xe2x80x2 and 102, 102xe2x80x2, and a pair of left and a pair of right hoisting accessory drums 103, 103xe2x80x2 and 104, 104xe2x80x2 are rotatably supported on the top of a gantry or portal body frame via pairs of clutches 105, 105xe2x80x2 and 106, 106xe2x80x2, respectively, and are rotationally drivable by a pair of left and a pair of right drive motors 107, 107xe2x80x2 and 108, 108xe2x80x2. A first pair of right and a first pair of left traverser wire ropes 109, 109xe2x80x2 and 110, 110xe2x80x2 have first ends taken up by the traverser drums 102, 102xe2x80x2 and 101, 101xe2x80x2 and have the other ends connected to pairs of right connecting portion 114 on a traverser 113, 113xe2x80x2 via pairs of right and left sheaves 111, 111xe2x80x2 and 112, 112xe2x80x2, respectively. Second pairs of right and left traverser wire ropes 115, 115xe2x80x2 and 116, 116xe2x80x2 have an end taken up by the traverser drums 102, 102xe2x80x2 and 101, 101, and have other ends connected to a pair of left connecting portions 119, 119xe2x80x2 on the traverser 113 via pairs of right and left sheaves 117, 117xe2x80x2 and 118, 118xe2x80x2, respectively. Furthermore, pairs of right and left hoisting accessory wire ropes 120, 120xe2x80x2 and 121, 121xe2x80x2 have first ends taken up by the hoisting accessory drums 104, 104xe2x80x2 and 103, 103xe2x80x2 and have the other ends passed over low-position rope pulleys 126, 126xe2x80x2 and 127, 127xe2x80x2 via right and left sheaves 122, 122xe2x80x2 and 123, 123xe2x80x2 and right and left sheaves 124, 124xe2x80x2 and 125, 125xe2x80x2 of the traverser 113, and then connected to connecting portions 128, 128xe2x80x2 and 129, 129xe2x80x2 of the traverser 113. From the rope pulleys 126, 126xe2x80x2 and 127, 127xe2x80x2, a hoisting accessory 130 capable of holding a container C is suspended. Hence, there is no need to provide rails and a trolley on the body frame. Since the weight on the body frame is reduced, the crane apparatus can be made compact and light-weight. Besides, the traverser 113, which supports the hoisting accessory 130, is supported by the wire ropes 109, 109xe2x80x2, 110, 110xe2x80x2, 115, 115xe2x80x2, 116, 116xe2x80x2 at the two separated connecting portions 114, 114xe2x80x2 and 119, 119xe2x80x2. Hence, sway of the hoisting accessory 130 and the suspended load C due to their inertial force is suppressed, and the work efficiency is increased.
In the conventional crane apparatus described above, let the weight of the hoisting accessory 130 and the suspended load C be W. Then, the rope tension T of the hoisting accessory wire ropes 120, 120xe2x80x2 and 121, 121xe2x80x2 will be:
T=W/4
The rope tensions T1R and T1L of the first traverser wire ropes 109 and 110, and the rope tensions T2R and T2L of the second traverser wire ropes 115 and 116 will be given by:
T1R=(W/2)cos xcex82/sin(xcex81+xcex82)xe2x88x92W/8
T1L=(W/2)cos xcex81/sin(xcex81+xcex82)xe2x88x92W/8
T2R=T1R
T2L=T1L
where xcex81 is the angle of each of the wire ropes 109, 115 and 120, and xcex82 is the angle of each of the wire ropes 110, 116 and 121.
In other words, the rope tensions T1R and T1L of the first traverser wire ropes 109, 109xe2x80x2 and 110, 110xe2x80x2, and the rope tensions T2R and T2L of the second traverser wire ropes 115, 115xe2x80x2 and 116, 116xe2x80x2 vary with the angle xcex81 of each of the wire ropes 109, 109xe2x80x2, 115, 115xe2x80x2 and 120, 120xe2x80x2, and the angle xcex82 of each of the wire ropes 110, 110xe2x80x2, 116, 116xe2x80x2 and 121, 121xe2x80x2, namely, the traversing position of the hoisting accessory 130. Whereas the rope tension T of each of the hoisting accessory wire ropes 120, 120xe2x80x2 and 121, 121xe2x80x2 is constant (W/4) regardless of the traversing position of the hoisting accessory 130.
Under these situations, when the hoisting accessory 130 is traversed most rightward, the hoisting accessory 130 stops at a position at which rightward and leftward horizontal components of force from the hoisting accessory wire ropes 120 and 121 are balanced, as shown in FIG. 5, because the rope tension T of the hoisting accessory wire ropes 120, 120xe2x80x2 and that of the hoisting accessory wire ropes 121, 121xe2x80x2 are the same. Thus, the hoisting accessory 130 cannot be brought fully close to a crane leg 131 which supports the sheaves 122, 122xe2x80x2, etc. As a result, the traversing range of the hoisting accessory 130 narrows. A full traversing function of the crane cannot be exhibited, and the work efficiency is low. If the position of the crane leg 131 is brought outward (rightward in FIG. 5), together with the sheaves 122, 122xe2x80x2, to enlarge the traversing range of the hoisting accessory 130, the apparatus will be upsized.
The present invention has been accomplished to solve the above-described problems with the earlier technology. It is an object of this invention to provide a crane apparatus designed to increase the work efficiency by enlarging the traversing range of a hoisting accessory without upsizing the apparatus.
A first aspect of the present invention, as a means of attaining the above object, is a crane apparatus comprising:
traverser drums and hoisting accessory drums rotatably mounted on a support and normally and reversely rotatable by drive motors;
a traverser having a pair of right and a pair of left connecting portions, and a pair of right and a pair of left sheaves thereon;
a right pair of and a left pair of rope pulleys positioned below the traverser;
a first pair of right and a first pair of left traverser wire ropes each having an end taken up by the traverser drums, and each having another end connected to the right pair of connecting portions of the traverser;
a second pair of right and a second pair of left traverser wire ropes having an end taken up by the traverser drums, and having another end connected to the left pair of connecting portions of the traverser;
a first pair of right and a first pair of left hoisting accessory wire ropes, each rope having an end taken up by the hoisting accessory drums, and having another end passed over one of the right pair of rope pulleys via one of the right pair of sheaves of the traverser and then connected to the traverser;
a second pair of right and a second pair of left hoisting accessory wire ropes, each rope having an end taken up by the hoisting accessory drums, and having another end passed over one of the left pair of rope pulleys via one of the left pair of sheaves of the traverser and then connected to the traverser;
a pair of right and a pair of left traverser sheaves and a pair of right and a pair of left hoisting accessory sheaves for guiding the right pair of wire ropes to be parallel and the left pair of wire ropes to be parallel; and
a hoisting accessory capable of attaching and detaching a load thereto and therefrom, and suspended from the right and left pair of rope pulleys.
Thus, the rope tension o f each of the hoisting accessory wire ropes varies with the traversing position of the hoisting accessory as does the rope tension of each of the traverser wire ropes. When the hoisting accessory comes to a terminal area in a traversing direction, the position at which the rightward and leftward horizontal components of force are balanced is more outward than in the earlier technology. Thus, the traversing range of the hoisting accessory widens. As noted from this, the traversing range of the hoisting accessory can be enlarged, and the work efficiency can be increased, without the need to upsize the apparatus.
In the crane apparatus as the first aspect of the invention, the hoisting accessory drums may be drivably connected to the drive motor, and the traverser drums may be drivably connected to the hoisting accessory drums via clutches. Consequently, the hoisting accessory drums may be driven independently to permit only the hoisting and lowering of the hoisting accessory.
A second aspect of the invention is a crane apparatus comprising:
traverser drums and hoisting accessory drums rotatably mounted on a support and normally and reversely rotatable by drive motors;
a traverser having a pair of right and a pair of left connecting portions, and a pair of right and a pair of left sheaves thereon;
a pair of right and a pair of left rotating drums suspended from the traverser;
a first pair of right and a first pair of left traverser wire ropes, each rope having an end taken up by the traverser drums, and each rope having another end connected to the right pair of connecting portions of the traverser;
a second pair of right and a second pair of left traverser wire ropes, each rope having an end taken up by the traverser drums, and each rope having another end connected to one of the left pair of connecting portions of the traverser;
a first pair of right and a first pair of left hoisting accessory wire ropes, each rope having an end taken up by the hoisting accessory drums, and each rope having another end passed over one of the right rotating drums via one of the right pair of sheaves of the traverser;
a second pair of right and a second pair of left hoisting accessory wire ropes, each rope having an end taken up by the hoisting accessory drums, and each rope having another end passed over one of the left pair of rotating drums via the left pair of sheaves of the traverser;
a pair of right and a pair of left traverser sheaves and a pair of right and a pair of left hoisting accessory sheaves for guiding the right pair of wire ropes to be parallel and the left pair of wire ropes to be parallel; and
a hoisting accessory capable of attaching and detaching a load thereto and therefrom, and connected to the respective pairs of right and left suspending wire ropes paid out from the respective right and left pair of rotating drums.
Thus, the rope tension of each of the hoisting accessory wire ropes varies with the traversing position of the hoisting accessory as does the rope tension of each of the traverser wire ropes. When the hoisting accessory comes to a terminal area in a traversing direction, the position at which the rightward and leftward horizontal components of force are balanced is more outward than in the earlier technology. Thus, the traversing range of the hoisting accessory widens. As noted from this, the traversing range of the hoisting accessory can be enlarged, and the work efficiency can be increased, without the need to upsize the apparatus.
In the crane apparatus as the second aspect of the invention, the hoisting accessory drums may be drivably connected to the drive motor, and the traverser drums may be drivably connected to the hoisting accessory drums via clutches. Consequently, the hoisting accessory drums may be driven independently to permit only the hoisting and lowering of the hoisting accessory.
In the crane apparatus as the second aspect of the invention, moreover, the hoisting accessory wire ropes and the suspending wire ropes may be passed over the rotating drum in opposite directions. Consequently, smooth actions can be performed.